The proposed work centers on study of certain features of cellular regulatory mechanisms which include the following: 1. The mechanism by which C-6 astrocytoma cells lose their ability to increase cAMP in response to norepinephrine after a 3 hr exposure to the neurohormone. 2. Characterization of an inducible form of cyclic nucleotide phoshodiesterase which accounts in part for the phenomenon mentioned in (1) above. 3. Evaluation of factors involved in the norepinephrine induced glycogenolysis which occurs in C-6 astrocytoma cells. 4. Elucidation of the mechanism by which papaverine inhibits cellular respiration.